Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$84.76	10.630%	$93.77	$93.77	$93.75	$93.80
Purchase #2	$221.81	13.526%	$251.812	$251.81	$251.80	$251.80
Purchase #3	$204.69	4.795%	$214.5049	$214.50	$214.50	$214.50
Purchase #4	$107.56	3.505%	$111.33	$111.33	$111.35	$111.30
Purchase #5	$40.56	7.210%	$43.4844	$43.48	$43.50	$43.50
Purchase #6	$56.64	4.491%	$59.1837	$59.18	$59.20	$59.20
Purchase #7	$39.99	12.648%	$45.0479	$45.05	$45.05	$45.00
7 purchase totals =	$756.01		$819.1329	$819.12	$819.15	$819.10